Filled polymeric compounds are prepared by mixing polymers with fillers such as silica, carbon black, and/or others. This can be done in what is known as a wet or a dry-mix procedure. Dry mixing is performed with little or no solvent, while the polymer is at melt state during mixing. Wet mixing is performed by combining polymer cement (polymer in solution) or a polymer emulsion with filler in suspension to form a polymer/filler mixture in a liquid media. Thereafter the mixture is dried to form a solution masterbatch.
Wet mixing generally produces good filler macro-dispersion since fillers and polymers are mixed to near uniformity before dried. However, the mixing energy and shear force during a wet mixing process is generally lower than a dry mixing process. Thus, the particle size of the filler dispersed in solution masterbatch from a wet-mix process is typically greater than in a dry-mix masterbatch. Larger particle sizes are not preferred in filled compounds for certain applications. Dry mixing processes provide an opportunity for smaller filler particle sizes, but such processes do not result in optimally dispersed filler.
The compounding of rubber by conventional means in tangential mixers, such as Banbury or Brabender mixers, requires a number of process stages in which raw rubber material in the form of bales undergoes intimate mixing with reinforcing fillers, and other common ingredients used in rubber compounding. Between the process stages, the mixtures are generally cooled on a batch-off system and then may be put into intermediate storage, prior to curing and tire building.